Infrared attenuation agent blends

ABSTRACT

Inorganic infrared attenuation agent blends have been developed to improve the thermal insulation properties of polymeric foams such as polystyrene low density foams. The inorganic infrared attenuation agent blends can include two or more metal oxides such as silicon dioxide, manganese (IV) oxide, iron (III) oxide, magnesium oxide, bismuth (III) oxide, cobalt oxide, zirconium (IV) oxide, molybdenum (III) oxide, titanium oxide, and calcium oxide. In some preferred embodiments, the inorganic infrared attenuation agent blends can include four or more of these metal oxides.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/105,004, filed on Aug. 20, 2018, which claims priority to and anybenefit of U.S. Provisional Patent Application No. 62/547,212, filedAug. 18, 2017, the contents of which are incorporated herein byreference in their entireties.

FIELD OF THE DISCLOSURE

The present invention relates to foamed polymeric insulating materialscontaining blends of inorganic infrared attenuation agents. Moreparticularly, it relates to foamed polymeric insulating materialscontaining blends of metal oxide infrared attenuation agents.

BACKGROUND

Polymeric foam is widely used as insulating material, and rigid foamedpolymeric boards are frequently used in building and constructionapplications to provide insulation to walls, floors, ceilings, and otherstructural components. The purpose of insulating materials is to preventor reduce the transfer of heat from an area of higher temperature to anarea of lower temperature.

The overall heat transfer in a typical foamed polymeric board can beseparated into three components: thermal conduction from gas (blowingagent) in the foam cells, thermal conduction from the polymer solids inthe foam, and thermal radiation across the foamed polymeric board. Ofthese three heat transfer components, thermal radiation provides about25% of the overall heat transfer. However, the transfer of heat throughthermal radiation can be modified by the use of infrared attenuatingagents.

An infrared attenuation agent (“IAA”) can be used to protect and improveinsulating materials, such as rigid foamed polymeric boards. Aneffective IAA increases absorption and re-emission of impinging heat,which decreases the transmission of heat radiation through theinsulating polymer foam. Traditionally, flake-like inorganic materialshave been used as IAAs, including, for example, graphite, aluminum,stainless steel, cobalt, nickel, carbon black, and titanium dioxide.

Unfortunately, individual inorganic IAAs may block only a narrow rangeof wavelengths in the IR spectrum. This means that IR radiation atwavelengths not blocked by the IAA is still transmitted across theinsulating layer. There is therefore a need for IAAs that block abroader range of IR wavelengths and provide sufficient levels of thermalresistance for use in insulating polymer foams.

SUMMARY

In accordance with the present disclosure, it has been found thatcertain blends of metal oxides can serve as effective infraredattenuation agents (IAA). Accordingly, in one aspect, the currentdisclosure provides an insulating polymer foam that includes a foamedpolymer comprising a) a polymer, b) a blowing agent, and c) an IAA blendcomprising two or more metal oxides selected from the group consistingof silicon dioxide, manganese (IV) oxide, iron (III) oxide, magnesiumoxide, bismuth (III) oxide, cobalt oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and calcium oxide. In someembodiments, the IAA blend comprising two or more metal oxides selectedfrom the group consisting of silicon dioxide, manganese (IV) oxide, iron(III) oxide, magnesium oxide, zirconium (IV) oxide, molybdenum (III)oxide, titanium oxide, and cobalt oxide. In some embodiments, the IAAblend comprises two or more metal oxides selected from the groupconsisting of silicon dioxide, manganese (IV) oxide, titanium oxide,iron (III) oxide, and magnesium oxide. In some embodiments, the IAAblend comprises four or more metal oxides selected from the groupconsisting of silicon dioxide, manganese (IV) oxide, iron (III) oxide,magnesium oxide, bismuth (III) oxide, cobalt oxide, zirconium (IV)oxide, molybdenum (III) oxide, titanium oxide, and calcium oxide.

In some embodiments, the IAA blend comprises at least 50% of the totalamount of infrared attenuation agents added to the insulating polymerfoam. In some embodiments, the IAA blend comprises, by weight: a) about0% to about 10% of metal oxides that absorb infrared radiation greaterthan 1500 cm⁻¹; b) about 10% to about 30% of metal oxides that absorbinfrared radiation from about 1500 cm⁻¹ to about 1200 cm⁻¹; c) about 20%to about 50% of metal oxides that absorb infrared radiation from about1200 cm⁻¹ to about 800 cm⁻¹; d) about 10% to about 30% of metal oxidesthat absorb infrared radiation from about 800 cm⁻¹ to about 500 cm⁻¹;and e) about 0% to about 10% of metal oxides that absorb infraredradiation less than 500 cm⁻¹. In some embodiments, the IAA blendcomprises from about 0.1 wt. % to 5 wt. % of the insulating polymerfoam. In some embodiments, the IAA blend further comprises pea starch.In some embodiments, the polymer is an alkenyl aromatic polymer, such aspolystyrene. In some embodiments, the insulating polymer foam has a cellsize greater than 50 microns. In some embodiments, the insulatingpolymer foam has a cell size in the range of from 50 to 300 microns.

In some embodiments, the present disclosure provides a rigid foaminsulating board made from a foamed polymer including an IAA blendcomprising two or more metal oxides selected from the group consistingof silicon dioxide, manganese (IV) oxide, iron (III) oxide, magnesiumoxide, bismuth (III) oxide, cobalt oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and calcium oxide. In someembodiments, the board has a thickness of between about ⅛ inch to about10 inches.

In another aspect, the present disclosure provides a method of preparingan insulating polymer foam having increased thermal resistance thatincludes the steps of: (a) providing a polymer; b) adding an IAA blendcomprising two or more metal oxides selected from the group consistingof silicon dioxide, manganese (IV) oxide, iron (III) oxide, magnesiumoxide, bismuth (III) oxide, cobalt oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and calcium oxide to thepolymer; c) melting the polymer to form a polymer melt; and d) extrudingthe polymer melt to form an insulating polymer foam. In someembodiments, the IAA blend comprises four or more metal oxides selectedfrom the group consisting of silicon dioxide, manganese (IV) oxide, iron(III) oxide, magnesium oxide, bismuth (III) oxide, cobalt oxide,zirconium (IV) oxide, molybdenum (III) oxide, titanium oxide, andcalcium oxide.

In some embodiments, the IAA blend comprises at least 50% of the totalamount of infrared attenuation agents added to the insulating polymerfoam. In some embodiments, the IAA blend comprises from about 0.1 wt. %to 3 wt. % of the insulating polymer foam. In some embodiments, thepolymer is an alkenyl aromatic polymer, such as polystyrene.

In another aspect, the current disclosure provides a foamable polymermaterial comprising a) a polymer, b) a blowing agent, and c) an IAAblend comprising two or more metal oxides selected from the groupconsisting of silicon dioxide, manganese (IV) oxide, iron (III) oxide,magnesium oxide, bismuth (III) oxide, cobalt oxide, zirconium (IV)oxide, molybdenum (III) oxide, titanium oxide, and calcium oxide. Insome embodiments, the IAA blend comprising two or more metal oxidesselected from the group consisting of silicon dioxide, manganese (IV)oxide, iron (III) oxide, magnesium oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and cobalt oxide. In someembodiments, the IAA blend comprises two or more metal oxides selectedfrom the group consisting of silicon dioxide, manganese (IV) oxide,titanium oxide, iron (III) oxide, and magnesium oxide. In someembodiments, the IAA blend comprises four or more metal oxides selectedfrom the group consisting of silicon dioxide, manganese (IV) oxide, iron(III) oxide, magnesium oxide, bismuth (III) oxide, cobalt oxide,zirconium (IV) oxide, molybdenum (III) oxide, titanium oxide, andcalcium oxide. In some embodiments, the IAA blend comprises at least 50%of the total amount of infrared attenuation agents in the foamablepolymer material. In some embodiments, the polymer is polystyrene.

BRIEF DESCRIPTION OF THE FIGURES

The present disclosure may be more readily understood by reference tothe following figures, wherein:

FIG. 1 provides an illustration of infrared radiation scattering by IAAparticles.

FIG. 2 graphically illustrates a spectrum showing the IR emissionintensity of an exemplary object at 25° C.

FIGS. 3A-3C graphically illustrate spectra showing the IR absorptionbands for individual metal oxides.

FIG. 4 graphically illustrates the thermal conductivity of exemplary XPSfoams including various inorganic IAAs.

FIG. 5 graphically illustrates the thermal conductivity of exemplary XPSfoams including metal oxide IAA blends.

FIG. 6 graphically illustrates the thermal conductivity of exemplary XPSfoams including metal oxide IAA blends and formed with HFC blowingagents.

DETAILED DESCRIPTION

The following discussion is presented to enable a person skilled in theart to make and use the present disclosure. Various modifications willbe readily apparent to those skilled in the art, and the generalprinciples disclosed herein may be applied to other embodiments andapplications without departing from the scope of the present disclosure.Thus, the present disclosure is not intended to be limited to theembodiments shown, but is to be accorded the widest scope consistentwith the principles and features disclosed herein.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure pertains. In case of conflict, thepresent specification, including definitions, will control.

The terminology as set forth herein is for description of theembodiments only and should not be construed as limiting. Unlessotherwise specified, “a,” “an,” “the,” and “at least one” are usedinterchangeably. Furthermore, as used in the Detailed Description andthe appended claims, the singular forms “a”, “an”, and “the” areinclusive of their plural forms, unless contraindicated by the contextsurrounding such.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

Insulating Polymer Foams

Thermal insulation reduces the transfer of heat between objects inthermal contact. Insulating polymer foams are popular thermal insulationmaterials, because of their desirable properties, including but notlimited to ease of manufacture, moldability, light weight, and thermalinsulating capacity.

Insulating polymer foams are mixtures of polymer and gas, where thepolymer forms a solid matrix that may enclose the gas in tiny gas-filledcells (closed-cell foam) and/or surround tiny tunnels from which the gasescapes (open-cell foam). The gas in the polymer mixture may come fromblowing agents, which are compositions that release gas upon certainconditions, such as pressure changes, temperature changes, chemicalreactions, and so forth. When the polymer and the blowing agent arecombined and treated under the appropriate conditions, the combinationmay create an insulating polymer foam. The insulating polymer foam mayalso include other components, such as processing aids, colorants, UVabsorbers, antioxidants, fire retardants, infrared attenuation agents,and other such additives, as are required for the specific function towhich the insulating polymer foam is intended.

Insulating polymer foams are used to provide thermal insulation indiverse applications, including but not limited to building insulation,food containers, hot or cold beverage cups, picnic coolers, shippingcontainers, etc.

Infrared Attenuation Agents

Thermal conductivity, k, is defined as the ratio of the heat flow percross-sectional unit of insulating material to the temperature drop perunit thickness. In metric units, the formula to calculate k is:

$k = \frac{W}{{m \cdot {^\circ}}\mspace{14mu} K}$where W=watts of power, m=mass of insulating material, and °K=temperature drop in degrees Kelvin. In Imperial units, the formula tocalculate k is:

$k = \frac{{Btu} \cdot {in}}{{{hr} \cdot {ft}^{2} \cdot {^\circ}}\mspace{14mu} F}$where Btu=heat in British Thermal Units, in=cross-sectional thickness ofinsulating material in inches, hr=hour, ft²=surface area of insulatingmaterial in square feet, and ° F.=temperature drop in degreesFahrenheit. The total thermal resistance R (i.e., R-value) is themeasure of the resistance to heat transfer, calculated as:R=t/kwhere t=the thickness of the insulating material.

The overall heat transfer in a typical insulating polymer foam board canbe separated into three components: thermal conduction from gas (blowingagent) in the foam cells, thermal conduction from the polymer solids inthe foam, and thermal radiation across the foamed polymeric board. Gasconvection within the cells is negligible due to the small cell sizespresent in typical insulating polymeric foam. See Schutz and Glicksman,J. Cellular Plastics, March-April, 114-121 (1984). For polymeric foammaterials, gas thermal conduction contributes about 60% of heat transferand solid conduction contributes about 15% of heat transfer. When thematerials for the blowing agent and the polymer matrix in the foamedpolymeric board are selected, the contributions of the two thermalconduction components to heat transfer are essentially fixed and aredifficult to modify. The remaining heat transfer component, thermalradiation, contributes about 25% of the overall heat transfer.

However, the transfer of heat through thermal radiation can be modifiedby the use of an infrared attenuating agent (“IAA”). The thermalconductivity, k, of a polymeric foam material can be reduced, and hencethe insulating effect provided by the foam can be increased, byincluding a suitable amount of an IAA in the polymeric foam material.Typically, these IAA materials are small particulates, less than about 1mm in size, made from various different materials including inorganicmaterials (e.g., aluminum oxide, clay particles), metals (e.g.,aluminum, gold, silver) and carbon-based materials (e.g., carbon black,graphite, expanded graphite, fibers made from carbon or graphite), etc.

FIG. 1 illustrates how IAAs modify the transfer of heat through apolymeric foam material. The polymeric foam material 10 comprisesparticles of an IAA material 20. Heat impinging on the polymeric foammaterial 10 is in the form of infrared (“IR”) radiation 30. When IRradiation 30 strikes the surface 12 of an object 10, a portion of the IRradiation 32 is reflected back into the environment and another portion34 is absorbed by the object and transformed into heat. Some of the heat34 absorbed by the object is re-emitted from the IAA particles 20 as IRradiation 36, a portion of which returns back to the environment throughthe surface 12 of the object 10. Some of the absorbed heat 34 andradiation 36 re-emitted from the IAA particles 20 eventually exits theother side of the object 10 as IR radiation 38. The IR radiation 38emitted by an object 10 is thus reduced by the presence of the IAAparticles 20. The IR radiation 38 emitted by an object 10 is a functionof its temperature. The wavelength of its peak intensity follows Wien'slaw, where the product of peak value wavelength and absolute temperatureare held constant. As the temperature range of interest for polymericfoams is typically around room temperature (i.e., 25° C.), this resultsin a peak intensity of IR radiation of about 1000 cm⁻¹, as seen in theIR spectrum illustrated in FIG. 2.

A common problem associated with insulating materials, such as rigidfoamed polymeric boards, is that they absorb IR radiation if the boardsare exposed to direct or reflected sunlight during buildingconstruction. The surface of each board that absorbs the IR radiationmay heat, but the heat is distributed unevenly through the thickness ofthe board because of the board's insulating properties. This unevenheating may cause the rigid foamed polymeric boards to warp, distort,curl, or otherwise change dimensionally during the construction process.Such dimensional changes may compromise the fit of the insulatingmaterials, which leads to gaps around the foam insulation and thereforereduced efficiency of the insulation within the completed building.

To effectively prevent this heating and uneven heat transference, aninorganic IAA may be added to the insulating polymeric foam. Withoutwishing to be bound by theory, IAA particles are believed primarily toabsorb impinging IR radiation, but an IAA particle may also reflect orrefract the IR radiation. A portion of the IR radiation absorbed by theIAA particle may convert to heat, which dissipates by conduction throughthe solid polymer matrix of the foam or the gaseous blowing agent in thefoam cells. It is believed that the remaining portion of the IRradiation absorbed by the IAA particle is re-emitted as IR radiationinto the area surrounding the IAA particle. The re-emitted IR radiationis spread uniformly in all directions around the IAA particle. Thismeans that a substantial portion (possibly around half) of there-emitted IR radiation is directed generally toward the original heatsource and away from the bulk of the polymeric foam material. Thiseffect reduces the overall heat absorption by the insulating polymerfoam material, and slows the overall rate of heat transfer through theinsulating polymer foam material, resulting in a lower macroscopicthermal conductivity.

Ideally, an IAA absorbs infrared radiation at all wavelengths of theinfrared emission spectrum, such as the IR spectrum shown in FIG. 2.Unfortunately, individual inorganic IAAs typically block only a narrowrange of wavelengths in the IR spectrum. This means that IR radiation atwavelengths not blocked by the IAA is still being absorbed andtransmitted across the insulating layer. The problems from unevenheating of rigid foamed polymeric boards (warping, distortion, curling,dimensional changes) may not be fully alleviated by individual inorganicIAAs.

It has been discovered that these problems may be avoided by usingcertain blends of metal oxides as the IAAs in the polymeric foaminsulation. Such metal oxide blends block a wide range of wavelengths inthe IR spectrum. Metal oxide IAA blends also effect a substantialreduction in the thermal conductivity of the insulating polymer foam,provided that a proper blend and sufficient amount of metal oxide IAAsare selected.

Metal Oxide Infrared Attenuation Agents

In accordance with this disclosure, blends of inorganic compounds, morespecifically blends of powdered inorganic metal oxides, have been foundto achieve a significant IR attenuation effect, because these blendsblock a wide range of the IR spectrum and promote a substantialreduction in the thermal conductivities of insulating polymer foams inwhich they are included. In some embodiments, the metal oxide IAA blendcomprises two or more metal oxides. In some embodiments, the metal oxideIAA blend comprises three or more metal oxides. In some embodiments, themetal oxide IAA blend comprises four or more metal oxides.

In some embodiments, the metal oxide IAA blend comprises at least 50% ofthe total IAA content in the insulating polymer foam. Other IAAs thatmay be used in the formulation of the insulating foam include, but arenot limited to, graphite, aluminum, stainless steel, gold, silver,cobalt, nickel, carbon black, and aluminum oxide. In some embodiments,the metal oxide IAA blend comprises about 50%-100% of the total IAAcontent in the insulating polymer foam, including about 60%-100%,including about 60%-95%, including about 60%-90% including about60%-85%, including about 60%-80%, including about 60%-75%, includingabout 60%-70%, including about 65%-100%, including about 65%-95%,including about 65%-90%, including about 65%-85%, including about65%-80%, including about 65%-75%, including about 70%-100%, includingabout 70%-95%, including about 70%-90%, including about 70%-85%,including about 70%-80%, including about 70%-75%, including about75%-100%, including about 75%-95%, including about 75%-90%, includingabout 75%-85%, including about 75%-80%, including about 80%-100%,including about 80%-95%, including about 80%-90%, including about80%-85%, including about 85%-100%, including about 85%-95%, andincluding about 85%-90% of the total IAA content in the insulatingpolymer foam.

It has unexpectedly been discovered that certain blends of metal oxideIAAs can be selected to absorb a broader range of IR radiation than ispossible with typical individual inorganic IAAs. FIGS. 3A-3C illustratespectra showing the regions of IR radiation absorbed by individual metaloxides. It should be noted that, within a given absorption range for agiven metal oxide, that metal oxide does not absorb the IR light evenlyat every wavelength number; instead, within a given range, theabsorption strength has peaks of great absorption and troughs of lessabsorption. However, by comparing the absorption spectra of variousmetal oxides, blends of the metal oxides can be selected where anabsorbance peak of one metal oxide overlaps the trough of another metaloxide.

Moreover, it has further been discovered that improved blocking of IRradiation can be obtained by blending two or more metal oxides from thegroup consisting of silicon dioxide, manganese (IV) oxide, iron (III)oxide, magnesium oxide, bismuth (III) oxide, cobalt oxide, zirconium(IV) oxide, molybdenum (III) oxide, titanium oxide, and calcium oxide.An exemplary metal oxide IAA blend includes two or more metal oxidesselected from the group consisting of silicon dioxide, manganese (IV)oxide, iron (III) oxide, magnesium oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and cobalt oxide. Anotherexemplary metal oxide IAA blend includes two or more metal oxidesselected from the group consisting of silicon dioxide, manganese (IV)oxide, titanium oxide, iron (III) oxide, and magnesium oxide. Yetanother exemplary metal oxide blend includes four or more metal oxidesfrom the group consisting of silicon dioxide, manganese (IV) oxide, iron(III) oxide, magnesium oxide, bismuth (III) oxide, cobalt oxide,zirconium (IV) oxide, molybdenum (III) oxide, titanium oxide, andcalcium oxide. However, the precise combination of metal oxides in themetal oxide IAA blend may be adjusted in consideration of such factorsas emission temperature of the insulating foam, relative absorptionstrength of the metal oxides, and availability and cost of the metaloxides.

As shown in FIG. 2, the IR emission spectrum of a heated object is notconstant but rather shows a bell-shaped distribution, with a peakemission at around 1000 cm⁻¹. To select the right amounts of each metaloxide in the metal oxide IAA blend, it may be necessary to use a largeramount of the selected metal oxides that absorb around the IRwavelengths where emission is large and a lesser amount of the selectedmetal oxides that absorb around the IR wavelengths where the emission issmall. Note that an individual metal oxide in the IAA blend may absorbIR emissions falling in two or more or more wavelength ranges. Table 1presents exemplary weight percentage distributions of metal oxides thatabsorb at different wavelength regions for an object at about 25° C.

TABLE 1 Exemplary Exemplary IR range of metal composition of Wavelengthoxides in IAA metal oxide IAA range (cm⁻¹) blend (wt. %) blend (wt.%) >1500  0-10 10 1500-1200 10-30 20 1200-800  30-50 40 800-500 10-30 20<500  0-10 10

The metal oxide IAA blend may comprise metal oxides that are ground intoa fine powder. This improves the homogeneous mixing of the metal oxideIAA blend into the polymer composition of the insulating foam. In someembodiments, the average particle size of the powdered metal oxide IAAblend may be from about 1 μm to about 100 μm, including from about 1 μmto about 50 μm, including from about 1 μm to about 25 μm, including fromabout 2 μm to about 50 μm, including from about 2 μm to about 25 μm,including from about 3 μm to about 50 μm, including from about 3 μm toabout 25 μm, including from about 4 μm to about 50 μm, including fromabout 4 μm to about 25 μm, including from about 5 μm to about 50 μm, andincluding from about 5 μm to about 25 μm. In some embodiments, theaverage size of the powdered metal oxide IAA blend may be from about 50nm to about 1 μm, including from about 50 nm to about 750 nm, includingfrom about 50 nm to about 500 nm, including from about 50 nm to about250 nm, including from about 50 nm to about 200 nm, including from about50 nm to about 150 nm, including from about 50 nm to about 100 nm,including from about 50 nm to about 75 nm, including from about 60 nm toabout 1 μm, including from about 60 nm to about 750 nm, including fromabout 60 nm to about 500 nm, including from about 60 nm to about 250 nm,including from about 60 nm to about 200 nm, including from about 60 nmto about 150 nm, including from about 60 nm to about 100 nm, includingfrom about 75 nm to about 1 μm, including about 75 nm to about 750 nm,including from about 75 nm to about 500 nm, including from about 75 nmto about 250 nm, including from about 75 nm to about 200 nm, includingfrom about 75 nm to about 150 nm, including from about 75 nm to about100 nm, including from about 90 nm to about 1 μm, including from about90 nm to about 750 nm, including from about 90 nm to about 500 nm,including from about 90 nm to about 250 nm, including from about 90 nmto about 200 nm, including from about 90 nm to about 150 nm, includingfrom about 90 nm to about 100 nm, including from about 100 nm to about 1μm, including from about 100 nm to about 750 nm, including from about100 nm to about 500 nm, including from about 100 nm to about 250 nm,including from about 100 nm to about 200 nm, including from about 100 nmto about 150 nm, including from about 125 nm to about 1 μm, includingfrom about 125 nm to about 750 nm, including from about 125 nm to about500 nm, including from about 125 nm to about 250 nm, including fromabout 125 nm to about 200 nm, including from about 125 nm to about 150nm, including from about 150 nm to about 1 μm, including from about 150nm to about 750 nm, including from about 150 nm to about 500 nm,including from about 150 nm to about 250 nm, including from about 150 nmto about 200 nm, including from about 200 nm to about 1 μm, includingfrom about 200 nm to about 500 nm, including from about 200 nm to about250 nm, including from about 250 nm to about 1 μm, including from about250 nm to about 750 nm, including from about 250 nm to about 500 nm.

The metal oxide IAA blend may be incorporated into the polymercomposition of the insulating foam at a concentration from about 0.1 wt.% to about 5 wt. % by weight of the polymer, including from about 0.1wt. % to about 3 wt. %, including from about 0.1 wt. % to about 2 wt. %,including from about 0.1 wt. % to about 1.5 wt. %, including from about0.1 wt. % to about 1 wt. %, including from about 0.1 wt. % to about 0.9wt. %, including from about 0.1 wt. % to about 0.8 wt. %, including fromabout 0.1% to about 0.7%, including from about 0.1 wt. % to about 0.6wt. %, including from about 0.1 wt. % to about 0.5 wt. %, including fromabout 0.1 wt. % to about 0.4 wt. %, including from about 0.2 wt. % toabout 5 wt. %, including from about 0.2 wt. % to about 3 wt. %,including from about 0.2 wt. % to about 2 wt. %, including from about0.2 wt. % to about 1.5 wt. %, including from about 0.2 wt. % to about 1wt. %, including from about 0.2 wt. % to about 0.9 wt. %, including fromabout 0.2 wt. % to about 0.8 wt. %, including from about 0.2% to about0.7%, including from about 0.2 wt. % to about 0.6 wt. %, including fromabout 0.2 wt. % to about 0.5 wt. %, including from about 0.2 wt. % toabout 0.4 wt. %, including from about 0.3 wt. % to about 5 wt. %,including from about 0.3 wt. % to about 3 wt. %, including from about0.3 wt. % to about 2 wt. %, including from about 0.3 wt. % to about 1.5wt. %, including from about 0.3 wt. % to about 1 wt. %, including fromabout 0.3 wt. % to about 0.9 wt. %, including from about 0.3 wt. % toabout 0.8 wt. %, including from about 0.3% to about 0.7%, including fromabout 0.3 wt. % to about 0.6 wt. %, including from about 0.3 wt. % toabout 0.5 wt. %, including from about 0.3 wt. % to about 0.4 wt. %,including from about 0.4 wt. % to about 5 wt. %, including from about0.4 wt. % to about 3 wt. %, including from about 0.4 wt. % to about 2wt. %, including from about 0.4 wt. % to about 1.5 wt. %, including fromabout 0.4 wt. % to about 1 wt. %, including from about 0.4 wt. % toabout 0.9 wt. %, including from about 0.4 wt. % to about 0.8 wt. %,including from about 0.4% to about 0.7%, including from about 0.4 wt. %to about 0.6 wt. %, including from about 0.4 wt. % to about 0.5 wt. %,including from about 0.5 wt. % to about 5 wt. %, including from about0.5 wt. % to about 3 wt. %, including from about 0.5 wt. % to about 2wt. %, including from about 0.5 wt. % to about 1.5 wt. %, including fromabout 0.5 wt. % to about 1 wt. %, including from about 0.5 wt. % toabout 0.9 wt. %, including from about 0.5 wt. % to about 0.8 wt. %,including from about 0.5% to about 0.7%, including from about 0.5 wt. %to about 0.6 wt. %, including from about 0.6 wt. % to about 5 wt. %,including from about 0.6 wt. % to about 3 wt. %, including from about0.6 wt. % to about 2 wt. %, including from about 0.6 wt. % to about 1.5wt. %, including from about 0.6 wt. % to about 1 wt. %, including fromabout 0.6 wt. % to about 0.9 wt. %, including from about 0.6 wt. % toabout 0.8 wt. %, including from about 0.6 wt. % to about 0.7 wt. %, andincluding from about 0.7 wt. % to about 5 wt. %, including from about0.7 wt. % to about 3 wt. %, including from about 0.7 wt. % to about 2wt. %, including from about 0.7 wt. % to about 1.5 wt. %, including fromabout 0.7 wt. % to about 1 wt. %, including from about 0.7 wt. % toabout 0.9 wt. %, including from about 0.7 wt. % to about 0.8 wt. %,including from about 0.8 wt. % to about 5 wt. %, including from about0.8 wt. % to about 3 wt. %, including from about 0.8 wt. % to about 1wt. %, including from about 0.9 wt. % to about 5 wt. %, including fromabout 0.9 wt. % to about 3 wt. %, including from about 0.9 wt. % toabout 1 wt. %, including from about 1 wt. % to about 5 wt. %, andincluding from about 1 wt. % to about 3 wt. %.

In certain embodiments, the insulating polymer foam may further comprisesuitable organic compounds, such as polysaccharides, which absorb IRradiation around 1000 cm⁻¹. Suitable polysaccharides include celluloseand starch. A specific example of a suitable polysaccharide is peastarch, which contains ˜35% amylose and ˜65% amylopectin having thefollowing structures:

Polymers Forming the Foams

Insulating polymer foams using the metal oxide IAA blends of thisdisclosure can be made from any polymer suitable for making insulatingpolymer foams. For example, they may be made from polyolefins,polyvinylchloride, polycarbonates, polyetherimides, polyamides,polyesters, polyvinylidene chloride, polymethylmethacrylate,polyurethanes, polyurea, phenol-formaldehyde, polyisocyanurates,phenolics, copolymers and terpolymers of the foregoing, thermoplasticpolymer blends, rubber modified polymers, and the like. Suitablepolyolefins include polyethylene and polypropylene, and ethylenecopolymers.

A particularly suitable class of thermoplastic polymers for making theinsulating polymer foams of this disclosure is alkenyl aromaticpolymers. Examples of alkenyl aromatic polymers include alkenyl aromatichomopolymers and copolymers of alkenyl aromatic compounds andcopolymerizable ethylenically unsaturated comonomers. The alkenylaromatic polymer material may further include minor proportions ofnon-alkenyl aromatic polymers. The alkenyl aromatic polymer material maybe comprised solely of one or more alkenyl aromatic homopolymers, one ormore alkenyl aromatic copolymers, a blend of one or more of each ofalkenyl aromatic homopolymers and copolymers, or blends of any of theforegoing with a non-alkenyl aromatic polymer.

Suitable alkenyl aromatic polymers include those derived from alkenylaromatic compounds such as styrene, α-methylstyrene, ethylstyrene, vinylbenzene, vinyl toluene, chlorostyrene, and bromostyrene. A particularlysuitable alkenyl aromatic polymer is polystyrene. A minor amount ofmonoethylenically unsaturated compounds such as C₂₋₆ alkyl acids andesters, ionomeric derivatives, and C₄₋₆ dienes may be copolymerized withalkenyl aromatic compounds. Examples of copolymerizable compoundsinclude acrylic acid, methacrylic acid, maleic acid, itaconic acid,acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate,isobutyl acrylate, n-butyl acrylate, methyl methacrylate, vinyl acetate,and butadiene. A particularly suitable alkenyl aromatic polymercomprises substantially (i.e., greater than about 95 percent)polystyrene, which polystyrene homopolymer being particularly preferred.

The polymers used to make the inventive foams may have a weight-averagemolecular weights of about 30,000 to about 500,000. Weight averagemolecular weights on the order of about 100,000 to 400,000 or even about120,000 to 300,000, are more interesting.

Combining the Metal Oxide IAA Blend with the Polymer

The metal oxide IAA blends can be combined with the polymer forming theinventive insulating polymer foams in any conventional manner. An amountfrom about 0.1% to about 5% by weight of metal oxide IAA blend can beincluded in the polymer.

In one approach, an in situ polymerization is used in which the monomersforming the polymer are polymerized after first being combined with themetal oxide IAA blends of this disclosure. This approach is especiallyeffective when the polymer forming the foam is made by additionpolymerization of ethylenically unsaturated monomers, especiallypolymers and copolymers of styrene, methyl methacrylate, or a mixture ofthese and/or other ethylenically unsaturated monomers. In some exemplaryembodiments, styrene monomer and an initiator (catalyst), such asbenzoyl peroxide (BPO), or 2,2′-azo-bis-isobutyronitrile (AIBN), areblended together completely using a conventional mixing apparatus suchas a homogenizer. The metal oxide IAA blend is then added to themonomer-initiator mixture in an amount from about 0.1% to about 5% byweight based on the weight of the polymer. After mixing, the mixture isheated in an oven at a temperature of about 60 to 100° C., for about 15to 30 hours for in-situ polymerization.

In mixing the metal oxide IAA blend with the monomer, as discussedabove, it is important to have uniform distribution of the metal oxideIAA blend. For example, the metal oxides comprising the IAA blend may beadded individually to the monomer, which is mixed thoroughly after eachaddition. Alternatively, uniform distribution may be achieved byvigorous mixing of the metal oxide IAA blend when it is added to themonomer before polymerization commences. Alternatively, the metal oxideIAA blend may be pre-blended with a polymeric carrier, such aspolystyrene, polymethyl methacrylate (PMMA), ethylene methacrylatecopolymer (EMA), to form an IAA masterbatch. The loading of the metaloxide IAA blend in can be as high as 70% by weight, including from 5% to60%, including from 10% to 50%, and including from 20% to 40% by weight,in such an IAA masterbatch. The IAA masterbatch may then be added to themonomer and mixed thoroughly before polymerization commences.

Another approach for combining the metal oxide IAA blends of thisdisclosure with the polymer forming the inventive insulating polymerfoams is physical blending in a melt-compounding process. This approachis especially useful when these polymers have a relatively low meltingor softening point. For example, the individual metal oxides comprisingthe IAA blend may be added individually to the softened or moltenpolymer used in the insulating foam, which is mixed thoroughly aftereach addition. Alternatively, the metal oxide IAA blend may be blendeddirectly into the softened or molten polymer used in the insulatingfoam, followed by thorough mixing. Alternatively, the metal oxide IAAblend may be pre-blended with a polymeric carrier, such as polystyrene,polymethyl methacrylate (PMMA), ethylene methacrylate copolymer (EMA),to form an IAA masterbatch. The loading of the metal oxide IAA blend canbe as high as 70% by weight, including from 5% to 60%, including from10% to 50%, and including from 20% to 40% by weight, in such an IAAmasterbatch. The IAA masterbatch is then blended with the softened ormolten polymer used in the insulating foam, and the masterbatch andpolymer are mixed thoroughly. Mixing may be conducted by any standardmethod know in the art. In some embodiments, the components are mixedusing a single screw or twin screw extruder.

In either approach, additional conventional additives such asplasticizers, flame retardant chemicals, pigments, elastomers, extrusionaids, antioxidants, fillers, antistatic agents, UV absorbers, citricacids, nucleating agents, surfactants, processing aids, etc., can beadded in conventional amounts to the polymer used in the insulatingfoam.

Forming the Insulating Polymer Foam

After in-situ polymerization or melt compounding, the polymer containingthe metal oxide IAA blend is foamed using a batch foaming process orstandard extrusion process. For example, extruded polystyrene foams canbe made by continuously extruding molten polystyrene containing ablowing agent under elevated temperature and pressure into ambient orvacuum conditions, allowing the mass to expand into lightweight,closed-cell foam. Standard extrusion processes and methods which may beused in the process of manufacturing embodiments of the presentdisclosure are described in commonly assigned U.S. Pat. No. 5,753,161which is herein incorporated by reference in its entirety.

Alternatively, the metal oxide IAA blend (as powdered individualcomponents, the powdered blend, or an IAA masterbatch) may be added tothe extruder separately from the polymer used in the insulating foam.The metal oxide IAA blend may be added to the extruder with the polymerin the same feeder port, or the metal oxide IAA blend may be added intothe extruder in a separate feeder port.

In the extrusion process, extruded insulating polymer foam containingthe metal oxide IAA blend may be prepared by single-screw, twin-screw,or tandem extruders with flat die and plate shaper or radial die andslinky shaper. The polymer (with or without the metal oxide IAA blend),the metal oxide IAA blend (if not previously incorporated with thepolymer), a blowing agent and, optionally, other additives are added tothe extruder to form a polymeric resin mixture.

The polymeric resin mixture, containing the organic IAA, polymer, andoptionally, other additives is heated to the melt mixing temperature andthoroughly mixed. The melt mixing temperature must be sufficient tosoften or melt the polymer. Therefore, the melt mixing temperature is ator above the glass transition temperature or melting point of thepolymer. In some embodiments, the melt mix temperature is from about160° C. to about 250° C., including from about 170° C. to about 220° C.

A blowing agent is then incorporated to form a foamable gel. Thefoamable gel is then cooled to a die melt temperature. The die melttemperature is typically cooler than the melt mix temperature,preferably from about 100° C. to about 140° C., and most preferably fromabout 110° C. to about 130° C. The die pressure must be sufficient toprevent pre-foaming of the foamable gel containing the blowing agent.Pre-foaming is the undesirable premature foaming of the foamable gelbefore extrusion of the foamable gel into a region of reduced pressure.Accordingly, the die pressure varies depending upon the identity andamount of blowing agent in the foamable gel. Preferably, the pressure isfrom about 50 bars to about 80 bars, more preferably about 60 bars. Theexpansion ratio (i.e., foam thickness per die gap width) is in the rangeof about 20 to about 70, typically about 60.

Any suitable blowing agent may be used in the practice on thisdisclosure. Blowing agents useful in the practice of this disclosureinclude inorganic agents, organic blowing agents, chemical blowingagents, and combinations thereof.

Exemplary aspects of the subject invention may utilize one or more of avariety of blowing agents to achieve the desired polymeric foamproperties in the final product. According to one aspect of the presentinvention, the blowing agent composition comprises one or more of: CO₂;halogenated blowing agents, such as hydrofluorocarbons (HFCs),hydrochlorofluorocarbons, hydrofluoroethers, hydrofluoroolefins (HFOs),hydrochlorofluoroolefins (HCFOs), hydrobromofluoroolefins,hydrofluoroketones, hydrochloroolefins, and fluoroiodocarbons; alkylesters, such as methyl formate; ethanol; water; and mixtures thereof. Inother exemplary embodiments, the blowing agent comprises one or more ofCO₂, ethanol, HFOs, HCFOs, HFCs, and mixtures thereof.

The hydrofluoroolefin blowing agents may include, for example,3,3,3-trifluoropropene (HFO-1243zf); 2,3,3-trifluoropropene; (cis and/ortrans)-1,3,3,3-tetrafluoropropene (HFO-1234ze), particularly the transisomer; 1,1,3,3-tetrafluoropropene; 2,3,3,3-tetrafluoropropene(HFO-1234yf); (cis and/or trans)-1,2,3,3,3-pentafluoropropene(HFO-1225ye); 1,1,3,3,3-pentafluoropropene (HFO-1225zc);1,1,2,3,3-pentafluoropropene (HFO-1225yc); hexafluoropropene (HFO-1216);2-fluoropropene, 1-fluoropropene; 1,1-difluoropropene;3,3-difluoropropene; 4,4,4-trifluoro-1-butene;2,4,4,4-tetrafluorobutene-1; 3,4,4,4-tetrafluoro-1-butene;octafluoro-2-pentene (HFO-1438);1,1,3,3,3-pentafluoro-2-methyl-1-propene; octafluoro-1-butene;2,3,3,4,4,4-hexafluoro-1-butene; 1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336mzz) or (HFO-1336mzz-Z); 1,2-difluoroethene (HFO-1132);1,1,1,2,4,4,4-heptafluoro-2-butene; 3-fluoropropene,2,3-difluoropropene; 1,1,3-trifluoropropene; 1,3,3-trifluoropropene;1,1,2-trifluoropropene; 1-fluorobutene; 2-fluorobutene;2-fluoro-2-butene; 1,1-difluoro-I-butene; 3,3-difluoro-I-butene;3,4,4-trifluoro-I-butene; 2,3,3-trifluoro-1-butene; I,1,3,3-tetrafluoro-I-butene; 1,4,4,4-tetrafluoro-1-butene;3,3,4,4-tetrafluoro-1-butene; 4,4-difluoro-1-butene; I, I,1-trifluoro-2-butene; 2,4,4,4-tetrafluoro-1-butene;1,1,1,2-tetrafluoro-2 butene; 1,1,4,4,4-pentafluorol-butene;2,3,3,4,4-pentafluoro-1-butene; 1,2,3,3,4,4,4-heptafluoro-1-butene;1,1,2,3,4,4,4-heptafluoro-1-butene; and1,3,3,3-tetrafluoro-2-(trifluoromethyl)-propene.

In some exemplary embodiments, the blowing agent comprises CO₂ and atleast one HFO with a global warming potential (GWP) less than or equalto 25. In some exemplary embodiments, the blowing agent blends includetrans-HFO-1234ze.

The blowing agent may also include one or more hydrochlorofluoroolefins(HCFO), such as HCFO-1233; 1-chloro-1,2,2,2-tetrafluoroethane(HCFC-124); 1,1-dichloro-1-fluoroethane (HCFC-141b);1,1,1,2-tetrafluoroethane (HFC-134a); 1,1,2,2-tetrafluoroethane(HFC-134); 1-chloro 1,1-difluoroethane (HCFC-142b);1,1,1,3,3-pentafluorobutane (HFC-365mfc);1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea); tnchlorofluoromethane(CFC-11); dichlorodifluoromethane (CFC-12); and dichlorofluoromethane(HCFC-22).

The term “HCFO-1233” is used herein to refer to alltrifluoromonochloropropenes. Among the trifluoromonochloropropenes areincluded both cis- and trans-3-chloro-1,1,1-trifluoro-propene(HCFO-1233zd or 1233zd). The term “HCFO-1233zd” or “1233zd” is usedherein generically to refer to 1,1,1-trifluoro-3-chloropropene,independent of whether it is the cis- or trans-form. The terms “cisHCFO-1233zd” and “trans HCFO-1233zd” are used herein to describe thecis- and trans-forms or trans-isomer of 1,1,1-trifluoro-3-chloropropene,respectively. The term “HCFO-1233zd” therefore includes within its scopecis HCFO-1233zd (also referred to as 1233zd(Z)), trans HCFO-1233zd (alsoreferred to as 1233(E)), and all combinations and mixtures of these.

In some exemplary embodiments, the blowing agent may comprise one ormore hydrofluorocarbons. The specific hydrofluorocarbon utilized is notparticularly limited. A non-exhaustive list of examples of suitableblowing HFC blowing agents include 1,1-difluoroethane (HFC-152a),1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane(HFC-134), 1,1,1-trifluoroethane (HFC-143a), difluoromethane (HFC-32),1,3,3,3-pentafluoropropane (HFO-1234ze), pentafluoro-ethane (HFC-125),fluoroethane (HFC-161), 1,1,2,2,3,3-hexafluoropropane (HFC 236ca),1,1,1,2,3,3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-hexafluoropropane(HFC-236fa), 1,1,1,2,2,3-hexafluoropropane (HFC-245ca),1,1,2,3,3-pentafluoropropane (HFC-245 ea), 1,1,1,2,3 pentafluoropropane(HFC-245eb), 1,1,1,3,3-pentafluoropropane (HFC-245fa),1,1,1,4,4,4-hexafluorobutane (HFC-356mff), 1,1,1,3,3-pentafluorobutane(HFC-365mfc), and combinations thereof.

Insulating Polymer Foams

The insulating polymer foams are rigid, closed cell foams exhibiting adensity of about 1.0 to about 5 pcf, more typically about 1.4 to about 3pcf, and a thermal conductivity of about 0.1 to about 0.3BTU·in/(hr·ft²·° F.), 0.14 to about 0.25 BTU·in/(hr·ft²·° F.), or about0.2 to BTU·in/(hr·ft²·° F.). Insulating polymer foams including themetal oxide IAA blends of the present disclosure preferably provideabout 0.5-2% lower conductivity compared with insulating polymer foamslacking an IAA. The insulating polymer foam can have a cell size rangingfrom 50 to 500 microns. In some embodiments, the insulating polymer foamhas an average cell size ranging from 50 to 400 microns, or from 100 to300 microns, or from 100 to 250 microns. Insulating polymer foams havingan average cell size greater than about 150 microns are particularlysuitable. The insulating polymer foam can be formed into a variety ofshapes, such as an insulating polymer foam board. Insulating polymerfoam board can be about ⅛ to 12 inches thick, but is more typicallyabout ½ to 4 inches thick.

In certain embodiments, the insulating polymer foam may have an R valuein the range of 3 to 8° F.·ft²·hr/BTU. In other embodiments, theinsulating polymer foam may have an R value in the range of 4 to 6°F.·ft²·hr/BTU. In certain embodiments, the insulating polymer foam maybe comprised of less than 50% by weight of a conventional inorganic IAA,wherein the conventional inorganic IAA is selected from the groupconsisting of graphite, aluminum, stainless steel, cobalt, nickel,carbon black, titanium dioxide, and combinations thereof. Furthermore,in certain embodiments, the insulating polymer foam having an R value inthe range of 3 to 8° F.·ft²·hr/BTU and comprised of a metal oxide IAAblend may be substantially free of a conventional inorganic IAA.

EXAMPLES

In order to more thoroughly describe embodiments of this disclosure, thefollowing working examples are provided. The following examples areprovided for illustrative purposes only and are in no way intended tolimit the scope of the disclosure.

Example 1: Polystyrene Foam Containing Metal Oxide IAAs with DifferentInfrared Absorption Wavelengths

Polystyrene foam samples containing three metal oxide IAA blends wereprepared. The composition of each metal oxide IAA blend is given inTable 2.

TABLE 2 Blend Blend Blend MO #1 MO #2 MO #3 Components (wt. %) (wt. %)(wt. %) Zirconium (IV) Oxide 80 20  4 Titanium (IV) Oxide 20 80 10Magnesium Oxide 40 Silicon Dioxide 20 Iron (III) Oxide 20 Manganese (IV)Oxide  3 Calcium Oxide  3

Three levels (0.2, 0.4, and 0.8 wt. %) of each metal oxide IAA blendwere melt blended into polystyrene in a twin screw extruder. As acontrol, polystyrene without an IAA was also prepared. Carbondioxide/ethanol was incorporated as the blowing agent and talc as thenucleating agent into the molten polystyrene mixture in the extruder.The compositions and certain properties for the sample foams areincluded in Table 3.

TABLE 3 Talc Blend Blend Blend cell Open Compressive MB MO#3 MO#1 MO#2CO₂ Ethanol Density size Cell strength Composition # (wt. %) (wt. %)(wt. %) (wt. %) (wt. %) (wt. %) (pcf) (mm) % (psi) Control 1 2 3.65 1.41.71 0.18 1.93 35.2 Example 1 2 0.2 3.65 1.4 1.73 0.19 0.96 34.5 Example2 2 0.4 3.65 1.4 1.73 0.18 1.76 32.7 Example 3 2 0.8 3.65 1.4 1.72 0.181.48 29.7 Control 2 0.78 3.3 2.25 1.81 0.23 3.64 31.5 Example 4 0.78 0.23.3 2.25 1.79 0.23 2.57 31.0 Example 5 0.78 0.4 3.3 2.25 1.80 0.23 2.7031.0 Example 6 0.78 0.8 3.3 2.25 1.80 0.24 2.25 30.5 Example 7 0.78 0.23.3 2.25 1.78 0.24 2.87 31.2 Example 8 0.78 0.4 3.3 2.25 1.77 0.24 3.5230.4 Example 9 0.78 0.8 3.3 2.25 1.78 0.24 2.88 30.6

Thermal conductivity as the foam samples aged was then recorded up to 60days. The 60-day thermal conductivities at each concentration of themetal oxides blends in the samples are shown in FIG. 4. As can be seen,not all metal oxides blends can reduce thermal conductivity. Blends MO#1 and MO #2 contain titanium oxide and zirconium oxide, and theirinfrared absorption bands overlap in the range of 400 to 900 cm⁻¹, asshown in FIG. 3. Foam thermal conductivity shows little or no reductionwith these two metal oxides blends. In comparison, blend MO #3 containsmore metal oxides, and these oxides cover a broader infrared wavelengthrange (400˜4000 cm⁻¹). As a result, foam thermal conductivity decreasesconsistently with increasing concentration of the metal oxide blend MO#3.

Example 2: Polystyrene Foam Containing Metal Oxide IAAs with DifferentInfrared Absorption Intensity

Polystyrene foam samples containing two blends of metal oxide IAAs wereprepared using the methods described for Example 1. Blend MO #6 alsoincluded pea starch, a polysaccharide, to evaluate the effect ofblending metal oxide IAAs with an organic IAA. The composition of eachIAA blend is given in Table 4.

TABLE 4 Blend Blend MO #6 MO #8 Components (wt. %) (wt. %) Pea Starch 20Silicon Dioxide 20 20 Zirconium (IV) Oxide 15 20 Aluminum Oxide 15 20Magnesium Oxide 15 20 Iron (III) Oxide 15 20

By following similar formulation and processing conditions as describedin example 1, the two blends MO #6 and MO #8 were added to XPS foam atfour levels (0.2, 0.4, 0.8, and 1.6 wt. %). The compositions and certainproperties for the sample foams are included in Table 5.

TABLE 5 Talc Blend Blend cell Open Compressive MB MO#6 MO#8 CO₂ EthanolDensity size cell Cell Strength Composition # (wt. %) (wt. %) (wt. %)(wt. %) (wt. %) (pcf) (mm) x:z % (psi) Control 3 2 3.65 1.4 1.78 0.180.75 0.97 42.13 Example 10 2 0.2 3.65 1.4 1.79 0.17 0.79 0.82 43.32Example 11 2 0.4 3.65 1.4 1.8 0.18 0.79 1.33 43.1 Example 12 2 0.8 3.651.4 1.78 0.17 0.79 1.02 42.82 Example 13 2 1.6 3.65 1.4 1.81 0.17 0.740.36 42.85 Example 14 2 0.2 3.65 1.4 1.77 0.18 0.84 1.39 39.62 Example15 2 0.4 3.65 1.4 1.77 0.18 0.84 2.12 38.28 Example 16 2 0.8 3.65 1.41.78 0.17 0.79 1.26 39.33 Example 17 2 1.6 3.65 1.4 1.78 0.17 0.78 1.1440.43

The results of thermal conductivity testing are shown in FIG. 5. As canbe seen, the thermal conductivity decreases with increasingconcentration of both MO #6 and MO #8 metal oxide IAA blends. Blend MO#6 has less decrease in thermal conductivities compared to blend MO #8,consistent with their infrared absorption capabilities. When metal oxideIAAs cover the same wavelength region of infrared absorption, the metaloxide IAA with higher absorption intensity will absorb more IR radiationand, hence, provide a lower thermal conductivity for the XPS foamcontaining that metal oxide IAA.

Example 3: Polystyrene Foam Containing Metal Oxide IAAs with HFCs

Polystyrene foam samples containing two blends of metal oxide IAAs wereprepared using the methods described for Example 1; however, for thisexample, the blowing agent was a 50/50 wt/wt blend of HFC-134a andHFC-152a. Metal oxide IAA blend MO #3 from Example 1 and two other metaloxide IAA blends were used in the foam samples. The composition of eachmetal oxides blend is shown in Table 6.

TABLE 6 Blend Blend Blend MO #3 MO #11 MO #17 Components (wt. %) (wt. %)(wt. %) Bismuth Oxide  5 Silicon Dioxide 20 20 40 Magnesium Oxide 40 15Iron (III) Oxide 20 20 20 Molybdenum Oxide 10 Calcium Oxide  3 Zirconium(IV) Oxide  4 10 Titanium (IV) Oxide 10 Aluminum Oxide 15 Manganese (IV)Oxide  3  5 40

By following similar formulation and processing conditions as describedin example 1, the three blends MO #3, MO #11, and MO #17 were added tothe XPS foam samples at two levels (0.4 and 0.8 wt. %). The compositionsand certain properties for the sample foams are included in Table 7.

TABLE 7 Talc Blend Blend Blend HFCs cell Open Compressive MB MO#3 MO#11MO#17 134a/152a Density size cell Cell Strength Composition # (wt. %)(wt. %) (wt. %) (wt. %) (wt. %) (pcf) (mm) x:z % (psi) Control 4 1.2 0 00 7.8 2.14 0.14 0.87 0.75 52.89 Example 18 0.9 0.4 7.8 2.03 0.16 1 0.5246.48 Example 19 0.9 0.4 7.8 2.02 0.16 1 0 44.75 Example 20 0.9 0.4 7.82.01 0.16 1 0 45.02 Example 21 0.6 0.8 7.8 1.98 0.17 1 0.02 42.69

The results of thermal conductivity testing are shown in FIG. 6. Again,the thermal conductivity was found to decrease with increasingconcentration of each metal oxide IAA blend when using HFCs as blowingagents.

Metal oxide IAA blends at concentrations around 0.4 wt. % were shown toreduce thermal conductivity by 0.001˜0.003 BTU·in/hr·ft²·° F., dependingon the components of the metal oxide IAA blend. When used in an XPS foamwith an R value of 5/in or a k value of 0.2 BTU·in/hr·ft²·° F., thisreduction is about 0.5 to 1.5% of total thermal conductivity. Thisdegree of thermal conductivity reduction is traditionally obtainedeither by increasing the foam density by about 0.2 pcf for a 1.5 pcfdensity foam, or by using about 1 to 2 wt. % more blowing agent over thenormal usage of about 8 wt. %, which increases costs of raw materials byabout 10%. For a PS foam with an R value of 4.2/in (0.2381BTU·in/hr·ft²·° F.) without the application of insulation blowing agents(HFCs or HFOs), as happens in the manufacture of EPS foams, the thermalconductivity improvement from using metal oxide IAA blends will be evenmore significant. In these applications, metal oxide IAA blends can helprealize about 3 to 8% of the necessary reduction from 0.2381 to 0.2BTU·in/hr·ft²·° F. to improve the R-value of an insulating board from R4.2/in to R 5.0/in, as required in the specification and building codes.

The complete disclosure of all patents, patent applications, andpublications, and electronically available materials cited herein areincorporated by reference. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. In particular,any theories of operation presented herein are optional and theinventors are therefore not bound by theories described herein.

What is claimed is:
 1. A method of preparing an insulating polymer foamhaving increased thermal resistance comprising the steps of: a)providing a polymer; b) adding an inorganic infrared attenuation agentblend comprising two or more metal oxides selected from the groupconsisting of silicon dioxide, zirconium (IV) oxide, magnesium oxide,iron (III) oxide, bismuth trioxide, manganese (IV) oxide, calcium oxide,molybdenum trioxide, vanadium pentoxide, and yttrium oxide to thepolymer; c) melting the polymer to form a polymer melt; and d) extrudingthe polymer melt to form an insulating polymer foam, wherein theinorganic infrared attenuation agent blend is present in an amount fromabout 0.1 to about 3 wt. %, based upon the total weight of theinsulating polymer foam.
 2. The method of claim 1, wherein the infraredattenuation agent blend comprises two or more metal oxides selected fromthe group consisting of silicon dioxide, manganese (IV) oxide, iron(III) oxide, bismuth (III) oxide, cobalt oxide, zirconium (IV) oxide,molybdenum (III) oxide, titanium oxide, and calcium oxide.
 3. The methodof claim 1, wherein the infrared attenuation agent blend comprises fouror more metal oxides selected from the group consisting of silicondioxide, manganese (IV) oxide, titanium oxide, and iron (III) oxide. 4.The method of claim 1, wherein the polymer comprises an alkenyl aromaticpolymer.
 5. The method of claim 1, wherein the infrared attenuationagent blend comprises at least 50% by weight of the total amount ofinfrared attenuation agents added to the insulating polymer foam.
 6. Themethod of claim 1, wherein the infrared attenuation agent blendcomprises, by weight: a) about 0% to about 10% of metal oxides thatabsorb infrared radiation greater than 1500 cm⁻¹; b) about 10% to about30% of metal oxides that absorb infrared radiation from about 1500 cm⁻¹to about 1200 cm⁻¹; c) about 20% to about 50% of metal oxides thatabsorb infrared radiation from about 1200 cm⁻¹ to about 800 cm⁻¹; d)about 10% to about 30% of metal oxides that absorb infrared radiationfrom about 800 cm⁻¹ to about 500 cm⁻¹; and e) about 0% to about 10% ofmetal oxides that absorb infrared radiation less than 500 cm⁻¹.
 7. Themethod of claim 1, wherein the infrared attenuation agent blend has anaverage particle size from about 1 μm to about 100 μm.
 8. The method ofclaim 1, further comprising a step of pre-blending the infraredattenuation agent blend with a carrier to form a masterbatch, prior tothe step of adding the infrared attenuation agent blend to the polymer.9. The method of claim 8, wherein the carrier comprises polystyrene,polymethyl methacrylate, ethylene methacrylate copolymer, orcombinations thereof.
 10. The method of claim 8, wherein the infraredattenuation agent blend comprises from about 5 to about 60 wt. % of themasterbatch.
 11. The method of claim 8, wherein the infrared attenuationagent blend comprises from about 10 to about 50 wt. % of themasterbatch.